The ZZ plant or Zamioculcas zamiifolia ranks among the most common houseplants around because of its good looks and its resilience. However, if you notice yellow leaves on your ZZ plant, it is important to immediately address the issue.
Why does your ZZ plant have yellow leaves? Overwatering is the most common reason for ZZ plants with yellow leaves. This requires immediate attention since it can lead to root rot. That said, yellow leaves can also be caused by underwatering, excess light, pests, too much fertilizer and nutrient deficiencies. Therefore, it is important to narrow down actual cause before applying treatment.
Reasons Why ZZ Plant Has Yellow Leaves
ZZ plants can take quite a bit of neglect making them perfect for beginners and anyone who has a very busy lifestyle.
They don’t need a lot of maintenance and are easy to care for.
However, when your ZZ plant has yellow leaves, it means something is not right. As such, it needs your attention and hopefully get treated as soon as possible.
Below are the most common reasons why your ZZ plant leaves are turning yellow and how to fix each issue.
Overwatering Can Cause ZZ Plant Yellow Leaves
Overwatering is the most common cause for your ZZ plant leaves turning yellow. Often, this will happen when there is a fungal infection and root rot.
Overwatering leads to root rot because it too much water causes the roots to drown in liquid for long periods of time. Unfortunately, roots need air just as they need water. And a balance of the two is required to keep a plant’s roots healthy.
When there is too much water, it prevents air from getting to the roots. What’s worse is that the damp environment leads to fungal growth.
This results in root rot with fungal infection.
Because the roots rot under the soil, you don’t see the process as it happens. Instead, you’ll only notice is when thing progress and the damage moves up to the stem and leaves.
This is what causes yellow leaves on ZZ plant.
So, when you see yellow leaves on your ZZ plant the first suspect is overwatering. That’s because it is the most common cause of yellow leaves. And it is also the most dangerous one since it can lead to root rot (which can kill your plant).
Verify that the plant is being overwatered by feeling the soil. If it feels wet, unpot the plant and check the roots of rotting.
If there if root rot, you need to take immediate action.
If there is no root rot, place the plant in a warm spot with bright, indirect light and good ventilation. They allow the soil to dry completely before you water the plant.
In case there is root rot, you will need to:
- Prune the rotted roots. Then prune the yellow leaves and any affected parts.
- If you pruned a more than 10% or 15% of the plant, proportionately prune the plant as well. This will reduce the size of the plant to give the few remaining roots a shot at survival and recovery.
- Carefully dispose of all the soil since they contain fungi. Remove as much soil from the roots as you can. Wash them off with water.
- Dip the entire root system in a solution of hydrogen peroxide and water. Use 1 tablespoon of hydrogen peroxide per cup of water. This will disinfect the roots.
- Also use the hydrogen peroxide solution to clean the pot to disinfect it.
- You can repot the new, smaller plant in a new pot or use the old one after it has been disinfected and dried. Use new, fresh, well-draining soil.
Underwatering Can Lead to Yellow Leaves in ZZ Plant
Underwater is another cause of yellow leaves in ZZ plants.
Along with the yellow leaves, you’ll see the plant droop, wilt or shrivel.
Because both overwatering and underwatering can lead to yellow leaves, it is very important to verify which is the actual cause.
Otherwise, you can worsen the situation.
For example, if your ZZ plant is suffering from overwatering and you add more water. Or if its underwatered then you let it dry out even more.
To make sure, always check the soil by feeling it.
If the soil feels wet, allow the soil to dry. In all likelihood the yellow leaves on ZZ plant here is caused by overwatering.
On the other hand, if the soil feels very dry, that means your ZZ plant is underwatered.
To fix this, water thoroughly so the root ball gets soaked. Then allow the soil to drain completely.
How Much Water Does the ZZ Plant Need?
Since overwatering and underwatering are quite problematic, it is important to understand how much moisture the plant really needs.
And the short and quick answer to this is not a lot.
As such, overwatering is much more prevalent than underwatering. In fact, it takes a good bit to underwater the plant.
You will usually need to let the soil go bone dry and add a little more time to that before the plant becomes underwatered. Thus, yellow leaves on ZZ plants due to underwatering happens less often.
But it can happen during hot weather or when you get very busy for like 2 to 4 weeks in a row and completely forget about the plant. This can easily happen especially when something important comes up in life.
In general, the ZZ plant does not need a lot of water.
To avoid overwatering, wait at least until the top 2 inches of soil has dried before adding more water.
If you want to play it a bit more safe, you can wait until the soil is 50% dry. That is, the top half of the soil has dried before you add water.
Some growers also let the soil dry out completely then water the plant. This works as well.
On average, it needs watering every 9 to 12 days or so. During the summer, it will need watering every 6-7 days and in the winter closer to once every 2 to 3 weeks.
The goals is not to water when the surface of the soil still feels moist. This will lead to overwatering.
As for underwatering, you can allow the soil to dry out completely. However, don’t leave it like that for the next 2 weeks or so. That’s when dehydration sets it as the plant becomes underwatered.
Too Much Light Will Make ZZ Plant Turn Yellow
Another reason why ZZ plants turn yellow is excess light exposure.
ZZ plants are quite tolerant when it comes to lighting. It does not mind low light and can tolerate bright conditions as well. But this light needs to be indirect, filtered or dapple light.
It cannot tolerate direct sunlight especially that during the hottest times of the day (10:30 a.m. to 3:30 p.m.). if you leave it under this kind of light, avoid doing so for more than 2, at most 3 hours a day.
Anything more than that, it is very likely that excess light exposure is the main cause of yellow leaves in your ZZ plant.
If this is the case, move the plant to a less bright spot.
The best way to tell is to check to make sure that the sun’s rays never touch the leaves of the plant at any given point during the day.
Nutrient Deficiency Also Causes Yellow Leaves in ZZ Plants
If you don’t feed your ZZ plant, this could very well be the reason it has yellow leaves.
That’s because yellow leaves in ZZ plants can be caused by nutrient deficiencies. As such, the plant does benefit from fertilizer. And it enjoys high quality fertilizer.
This way, it gets the essential nutrients N-P-K (nitrogen, phosphorus and potassium) along with the other secondary and trace minerals. All of these will prevent yellow leaves (and in some cases pale colored foliage).
At the minimum, try to feed your plant at least once or twice a year if you suspect nutrient deficiency is the cause of the yellow leaves.
This will prevent your ZZ plant from turning yellow.
On the other hand, yellow leaves can likewise be caused by excess fertilizer.
So, it is important that you give the plant nutrients. But avoid giving it too much.
The reason is that commercial fertilizers contain salts.
So, when you feed your plant, you’re not only giving them nutrients, you are giving them salt as well. Unfortunately, plants hate salt.
But these salts will keep building up in the soil. After a while, they will become toxic to the roots and damage them.
As such, while fertilizer is good don’t give the plant more than what it needs.
In general, the ZZ plant only needs to be fed once a month during its growing season which occurs in spring and summer. You do not need to feed in the fall or winter.
Also dilute each application so you don’t use more than half the suggested strength on the instructions. That’s because potted plants indoors don’t need as much of a dose as those outdoors in the ground.
To make sure that excess salts don’t burn your plant’s roots, you can flush the soil if you suspect over fertilizing. This will allow the water to carry the salts along with excess minerals that have been left in the soil away.
ZZ plants have good resistance to pests when they are healthy. It is also a good idea to clean its leaves to remove dust since bugs are attracted to dust.
However, when your plant is stressed, weak or ill, it becomes susceptible to insects. And they can sense this, and this is when they take the opportunity to pounce.
The most common pests that attack ZZ plants include spider mites, mealybugs and aphids. These are sap sucking insects that feed by taking the plant’s sap or internal juices.
Sap contains water and nutrients that is supposed to get circulated to the leaves. So, when enough pests feed and take more sap, they rob your ZZ plant of water and nutrients.
As a result, it will experience some deficiency and water loss. And the larger the infestation the more damage they will cause.
This is why when these bugs are present, you’ll see yellow patches occur. Some leaves will turn completely yellow. On the other hand, you can see brown spots which get bigger along with holes as well.
Because they can grow in population very quickly, it is important to regularly check for pests. These are very tiny so I do suggest in using a magnifying glass.
The bugs like to hide on the undersides of the leaves and the nooks and crannies. So, make sure to check those.
If you see any, immediately treat the plant with insecticidal soap or neem oil.
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Like its other features, the ZZ plant tolerates a wide range of climate conditions. It will do well as long as you keep temperature between 55 to 90 degrees Fahrenheit.
This makes it easy to care for indoors in homes and offices.
However, it is less tolerant of the cold since it is a tropical plant. Therefore, avoid leaving it in environments that are colder than 50 degrees Fahrenheit.
It will struggle there, and growth will slow. Its leaves can also turn yellow as a result.
This is why is it is best suited for USDA Hardiness Zones 9 and 10. It can live outdoors all year long in these locations because the winters are warm and sunny with no snow or frost.
In contrast, make sure to move the plant indoors if you bring it outdoors for the summer anywhere colder (below Zone 9). It won’t be able to take the cold of winter in these regions.
Similarly, temperature fluctuations can cause leaves to turn yellow as well. So, avoid any spot where the temperature can dramatically change or jump and down every so often.
If you notice that your ZZ plant has yellow leaves and is staying somewhere colder than 50 degrees Fahrenheit, move it to a warmer, cozier spot. This should fix the issue.